1. Field of the Invention
This invention relates to electricity generation for pedalled vehicles and more particularly to improvements in the generation of electricity by pedal power and its use in contributing to road safety.
2. Description of the Prior Art
Pedalled vehicles such as bicycles are particularly vulnerable to road accidents not only because they offer little or no protection to the rider but primarily because the drivers of other vehicles may not see them, especially in the dark or poor weather conditions. It is of course mandatory in most countries for bicycles to use lights in the dark and most are equipped with reflectors, but conventional lighting systems leave much to be desired. If lighting is by dry batteries these may fail or the rider may simply fail to turn them on. The drawbacks of conventional generators, either incorporated in a wheel hub or driven by a tyre, include the fact that they make pedalling harder, which is a disincentive to using them, and that the illumination they provide ceases as soon as the bicycle stops, representing a considerable danger e.g. when the bicycle is waiting at traffic lights or at a road junction. Reflectors are of course only effective when illuminated by the oncoming vehicle, which will not occur if the latter has no adequate lights or is approaching at an angle.
In recent years LEDs (light emitting diodes) have been used either instead of or to supplement light bulbs. Taking advantage of their relatively low power consumption it is practicable to have them permanently in use, even in daylight. Flashing LEDs attract attention and it has been appreciated that it is particularly advantageous to mount them upon the pedals. Their rotary motion attracts attention and moreover an oncoming driver can judge his orientation relative to the bicycle by whether the rotating LEDs describe a circle (when at right angles) a vertical line (when in front or behind) or an elipse when approaching at an angle. Direction can of course be judged by the colour of the visible LEDs, usually red indicating the rear of the bicycle and a white or green light indicating that it is approaching.
While the use of LEDs on the pedals of a bicycle is highly advantageous, if their power is derived from a dry battery this may fail unbeknownst to the rider and in any event the use of dry batteries is undesirable if it can be avoided both because of their high cost and the environmental problems associated with their disposal.
Japanese Patent Publication No. 07291174A and U.S. Pat. No. 5,662,405 propose the modification of a bicycle pedal to serve as a generator of electricity to illuminate LEDs mounted on the frame or tread portion of the pedal. Permanent magnets are attached to the pedal shaft or spindle and the pedal frame or tread portion is provided with windings or solenoids and relative rotation between the permanent magnets and the windings as relative rotation occurs between the pedal spindle and tread portion generates current by magnetic induction on the same principles as in the case of a conventional bicycle dynamo.
The voltage generated by an inductance generator is a function of the number of windings of the stator and the speed of rotation of the rotor. The essential weakness of a system such as described in the said Japanese patent publication resides in the relatively very low speed of rotation of the rotor or spindle under normal circumstances. A pedal spindle will rotate only once relative to the tread portion or frame mounted upon it for every revolution of the crank on which the spindle is mounted. A cyclist typically will pedal at between 30 and 60 revolutions of the pedal crank per minute. Japanese Patent publication No. 07291174A recognises this problem but the only solution proposed is to increase the number of windings. The present Applicants have calculated that this is impracticable because it would increase unacceptably the cost and/or size of the stator component, bearing in mind that this is to be incorporated in the tread portion of a pedal.
Another disadvantage of using the pedal spindle itself as the rotor is that it, and the associated bearings, will be subjected to the wear and abuse in service which pedal spindles usually experience. It is preferable that the relatively delicate and accurate bearings of a generator should not be directly exposed to such treatment.